Holding apparatus, holding method, exposure apparatus and device manufacturing method

ABSTRACT

A reticle holder  18  has; a first suction section  63  facing a precision warrantable area AR 1  having a predetermined surface precision, of a lower face Ra of a reticle R; a second suction section  64  facing a precision unwarrantable area AR 2  outside of the precision warrantable area AR 1;  a pore  70   a  connected to a suction apparatus which draws out gas in a space between the lower face Ra of the reticle R and the first suction section  63,  and a pore  70   b  connected to the suction apparatus  72  which draws out gas in the space between the lower face Ra of the reticle R and the second suction section  64.  As a result, the reticle can be held stably, without deteriorating the surface precision of the precision warrantable area.

[0001] This application is a continuation of PCT/JP02/01200 filed onFeb. 13, 2002, and priority is claimed under 35 U.S.C. §119 to Japanesepatent application No. 2001-036130 filed on Feb. 13, 2001, which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a holding apparatus and aholding method, and an exposure apparatus which uses a mask and asubstrate held by the holding apparatus to expose a mask pattern ontothe substrate. More specifically, the present invention relates to aholding apparatus and a holding method, an exposure apparatus and adevice manufacturing method, suitable for use in a lithography process,particularly when devices such as liquid crystal display elements andsemiconductor elements are manufactured.

[0004] 2. Background Art

[0005] In the lithography process, being one of the manufacturingprocesses for semiconductor devices, various kinds of exposure apparatushave been used, which transfer a circuit pattern formed on a mask or areticle (hereinafter referred to as a “reticle”) onto a substrate suchas a wafer or a glass plate, to which a resist (photosensitizer) hasbeen applied. For example, as an exposure apparatus for semiconductordevices, a reduced size projection exposure apparatus is mainly used,which transfers the reticle pattern onto the wafer while reducing thesize of the pattern, using a projection optical system, corresponding tothe miniaturization of the minimum line width of the pattern (devicerule) accompanying recent high integration of integrated circuits.

[0006] In the above described exposure apparatus, when the reticlepattern is transferred onto the wafer, the reticle is held on a reticleholder by vacuum attraction. As a conventional example of such a reticleholder, there is one shown in FIG. 26. FIG. 26 is a perspective viewillustrating a reticle holder for holding a reticle. As shown in thisfigure, the reticle holder 100 comprises an opening 102 formed at thecenter, seat portions 104 provided at a plurality of positions (threeplaces) on the upper face, and suction pads 106 respectively provided onthe upper faces of the seat portions 104. The reticle holder 100 isprovided so as to be movable two-dimensionally in XY directions withrespect to a base 110. The suction pads 106 are provided at positionsfacing the lower face of the reticle R, and connected to a compressor(suction apparatus) which is not shown. The compressor draws out gas inthe space between the lower face of the reticle R and the suction pads106 to make the pressure in the space between the lower face of thereticle R and the suction pads 106 lower than the outside pressure, sothat the reticle R is attracted and held by the reticle holder 100.

[0007] The reticle R has a pattern at the center on the lower face, anda pellicle PE for protecting a pattern face is provided on the patternface (that is, the central part on the lower face of the reticle R).Therefore, the reticle holder 100 should attract and hold the portionsof the lower face of the reticle, except of the portion where thepellicle PE is provided.

[0008] It is preferable that the contact surface between the suctionpads 106 of the reticle holder 100 and the reticle R is large, in orderthat the reticle holder 100 stably holds the reticle R. However, asdescribed above, the size (area) of the face of the reticle R which isattracted by the reticle holder 100 is restricted by the pellicle PE. Ifit is tried to attract and hold a wide area of the portion other thanthe pellicle PE, on the lower face of the reticle R, even an area, whichdoes not have a predetermined surface precision, for example, an outerperipheral area on the lower face of the reticle R (hereinafter referredto as “precision unwarrantable area”) must be attracted and held by thereticle holder 100. In this case, the contact surface of the reticle Rwith respect to the suction pads 106 is distorted, and this distortionaffects even the area having predetermined surface precision(hereinafter referred to as a “precision warrantable area”) to decreasethe surface precision, thereby causing a problem in that high precisionexposure processing cannot be performed.

[0009] On the other hand, it can be considered to attract and hold thearea in the vicinity of the pellicle PE (hereinafter referred to as an“inside edge area”), being the precision warrantable area, in theportion other than the pellicle PE on the lower face of the reticle R.However, when the reticle holder 100 holds this inside edge area, thereticle holder 100 interferes with a carrier device which loads andunloads the reticle R with respect to the reticle holder 100, which isnot desirable. In other words, when the reticle R is loaded or unloadedwith respect to the reticle holder 100, a carrier device having a forkportion is used. However, when the reticle R is supported by this forkportion, the fork portion supports the portion other than the pelliclePE on the lower face of the reticle R. When the reticle R is loaded orunloaded with respect to the reticle holder 100 by using this carrierdevice, the shape or the size of the seat portion 104 of the reticleholder 100, or the position or the size of the suction pads 106 arerestricted, in order to prevent interference between the reticle holder100 and the fork portion, and as a result, the position and size of thesurface to which the reticle R is attracted are also restricted.

[0010] Moreover, it can be also considered to attract and hold only theprecision warrantable area existing in an area where interference withthe carrier device does not occur, which is the portion other than thepellicle PE on the lower face of the reticle R. However, in this case,since the surface of the reticle R to be attracted becomes small, theholding power of the reticle holder 100 with respect to the reticle Rbecomes weak. For example, when the reticle holder 100 is shifted withrespect to the base 110 at high speed, there is the possibility that thereticle R on the reticle holder 100 is deviated due to the inertiaforce. When the surface of the reticle R to be attracted is small, itcan be considered to increase the attractive force by the compressor, toincrease the holding power with respect to the reticle R. However, inthis case, since a local force acts on the reticle R, the reticle R maybe distorted.

[0011] In view of the above situation, it is an object of the presentinvention to provide a holding apparatus and a holding method that canhold a reticle (mask) stably, without deteriorating the surfaceprecision in the precision warrantable area, and an exposure apparatusthat can perform accurate exposure processing with this holdingapparatus, and a device manufacturing method that can manufacturedevices highly accurately.

BRIEF SUMMARY OF THE INVENTION

[0012] A first aspect of the present invention is a holding apparatuswhich holds a surface to be attracted of a flat sample. This holdingapparatus comprises; a first holding section facing a first area havingpredetermined surface precision of the surface to be attracted, a secondholding section facing a second area other than the first area of thesurface to be attracted, and a suction apparatus which draws out gas inspaces between the surface to be attracted and the first and the secondholding sections.

[0013] The suction apparatus may comprise; a first suction device whichdraws out gas in a space between the surface to be attracted and thefirst holding section, and a second suction device which draws out gasin a space between the surface to be attracted and the second holdingsection.

[0014] A second aspect of the present invention is a holding method forholding a surface to be attracted of a flat sample. By this holdingmethod, each of a first area having a predetermined surface precision ofthe surface to be attracted and a second area other than the first areaof the surface to be attracted are attracted and held by a first holdingsection and a second holding section, respectively and independently.

[0015] According to the apparatus and the method described above, thefirst area having predetermined surface precision of the surface to beattracted and the second area other than the first area of the surfaceto be attracted are attracted and held by the first holding section andthe second holding section, respectively and independently. Accordingly,the first holding section can stably hold the sample, withoutdeteriorating the overall surface precision of the sample, and thesecond holding section can increase the size of the whole surface of thesample to be attracted. As a result, stable retention can be realized.

[0016] Each of the first holding section and the second holding sectionmay be arranged at a plurality of positions with respect to the surfaceto be attracted. In this case, the sample can be held more stably.

[0017] The first holding section and the second holding section may bearranged adjacent to each other, and a boundary portion between thefirst holding section and the second holding section may be arranged atleast in the first area of the sample. In this case, even if the sampledeforms to bend, peeling of the sample from the first holding sectioncan be suppressed. As a result, the holding apparatus can stably holdthe sample.

[0018] The second holding section and the second area of the sample maybe set to have a predetermined gap. In this case, the attraction of thesecond holding section with respect to the second area becomes smallerthan that of the first holding section with respect to the first area.Therefore, deformation of the sample resulting from the second holdingsection attracting the second area with a strong attraction can besuppressed.

[0019] The suction amount of the gas per unit time by the first suctiondevice and the suction amount of the gas per unit time by the secondsuction device may be controlled. In this case, the attraction of thesecond holding section with respect to the second area can be madesmaller than that of the first holding section with respect to the firstarea, thereby suppressing the deformation of the sample resulting fromthe second holding section attracting the second area with a strongattraction.

[0020] The area of the first holding section with respect to the firstarea may be set larger than the area of the second holding section withrespect to the second area. In this case, since the attraction of thesecond holding section with respect to the second area can be made lessthan that of the first holding section with respect to the first area,deformation of the sample resulting from the second holding sectionattracting the second area with a strong attraction can be suppressed.

[0021] A third aspect of the present invention is an exposure apparatuswhich exposes a pattern of a mask held by a mask holder onto a substrateheld by a substrate holder. This exposure apparatus uses the holdingapparatus for at least one of the mask holder and the substrate holder.

[0022] According to the exposure apparatus of the present invention, theexposure processing can be performed, while stably holding the mask orsubstrate, with the mask or substrate maintained at predeterminedsurface precision. As a result, highly accurate exposure processing canbe realized.

[0023] An other aspect of the present invention is a devicemanufacturing method incorporating a lithography process, and theexposure apparatus is used in the lithography process.

[0024] According to the device manufacturing method of the presentinvention, since this uses the exposure apparatus which can performstable exposure processing with high accuracy, with the mask orsubstrate maintained at predetermined surface precision, high qualitydevices can be manufactured.

[0025] An other aspect of the present invention is a mask holding methodfor holding a mask in which a surface to be attracted has a convex shapetowards a first direction within a predetermined allowable range, with apair of first attraction holding sections arranged opposing the firstdirection. In this method, the mask is held so as to satisfy thefollowing relational expression:

δ<Pl ₁ ²(2l ₁+3l ₂)/6EI

[0026] where l₁ respectively denotes an interval between a centralsupporting point and an outside supporting point of the mask in therespective attraction holding sections, l₂ denotes an interval betweenthe central supporting points in the respective attraction holdingsections, 6 denotes an interval between the mask and the outsidesupporting point, which is generated when the mask is mounted on thecentral supporting point, P denotes a product of the atmosphericpressure and an attraction area of the first attraction holding section,E denotes a modulus of longitudinal elasticity of the mask, and Idenotes a geometrical moment of inertia of the mask.

[0027] An other aspect of the present invention is a mask holdingapparatus which holds a mask in which a surface to be attracted has aconvex shape towards a first direction within a predetermined allowablerange, with a pair of first attraction holding sections arrangedopposing the first direction. In this apparatus, the first attractionholding sections are respectively arranged so as to satisfy thefollowing relational expression:

δ<Pl ₁ ²(2l ₁+3l ₂)/6EI

[0028] where l₁ respectively denotes an interval between a centralsupporting point and an outside supporting point of the mask in therespective attraction holding sections, l₂ denotes an interval betweenthe central supporting points in the respective attraction holdingsections, δ denotes an interval between the mask and the outsidesupporting point, which is generated when the mask is mounted on thecentral supporting point, P denotes a product of the atmosphericpressure and an attraction area of the first attraction holding section,E denotes a modulus of longitudinal elasticity of the mask, and Idenotes a geometrical moment of inertia of the mask.

[0029] According to the method and apparatus described above, the firstattraction holding sections can hold the mask stably, withoutdeteriorating the overall surface precision of the mask, and increasethe size of the whole surface of the mask to be attracted. As a result,stable mask retention can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030]FIG. 1 is an overall schematic diagram illustrating one embodimentof an exposure apparatus having a holding apparatus of the presentinvention.

[0031]FIG. 2 is a perspective drawing of a stage apparatus having theholding apparatus constituting the exposure apparatus.

[0032]FIG. 3 is a perspective drawing of the holding apparatus of thepresent invention.

[0033]FIG. 4 is an enlarged perspective view of the main part in oneembodiment of the holding apparatus of the present invention.

[0034]FIGS. 5A and 5B are schematic diagrams illustrating a state with amask held by the holding apparatus of the present invention, whereinFIG. 5A is a top view and FIG. 5B is a sectional view as seen in thedirection of arrows A-A.

[0035]FIG. 6 is an enlarged sectional view of the main part, when themask is held by the holding apparatus of the present invention.

[0036]FIG. 7A to FIG. 7D are diagrams for explaining a relation betweenthe shape of a mask held by the holding apparatus and deformationthereof.

[0037]FIG. 8 is a table showing the relation between the size andinterval of a second area and a maximum deflection of the mask.

[0038]FIG. 9 is a graph obtained by changing the table in FIG. 8 to agraphical representation.

[0039]FIG. 10 is a sectional view indicating another example of the maskof the present invention.

[0040] FIGS. 11 to 14 are enlarged perspective views of the main part inother embodiments of the holding apparatus of the present invention.

[0041]FIG. 15 is a perspective view illustrating another embodiment ofthe holding apparatus of the present invention.

[0042]FIG. 16 is a perspective view showing a state with a reticle beingattracted, in the embodiment.

[0043] FIGS. 17 to 21 are enlarged sectional views of the main part,when the mask is held by the holding apparatus of the present invention.

[0044] FIGS. 22 to 24 are sectional views of a reticle for explainingthe effects of other embodiments of the present invention.

[0045]FIG. 25 is a flowchart for explaining one example of asemiconductor device manufacturing process.

[0046]FIG. 26 is a perspective drawing of a conventional holdingapparatus.

DETAILED DESCRIPTION OF THE INVENTION

[0047] Hereunder is a description of preferred embodiments of thepresent invention, with reference to the drawings. However, the presentinvention is not limited to the respective embodiments, and for example,the components in these embodiments may be appropriately combined.

[0048] At first, a first embodiment of the holding apparatus and theexposure apparatus of the present invention will be described, withreference to FIGS. 1 to 6. FIG. 1 is an overall schematic diagram of theexposure apparatus, and FIG. 2 is a perspective drawing of a reticlestage having a reticle holder (holding apparatus, mask holder)constituting the exposure apparatus. FIG. 3 is a perspective drawing ofthe reticle holder, and FIG. 4 is an enlarged view of the main part ofthe reticle holder. FIGS. 5A and 5B are schematic diagrams illustratinga state with a reticle held by the reticle holder, wherein FIG. 5A is atop view and FIG. 5B is a sectional view as seen in the direction ofarrows A-A. FIG. 6 is an enlarged sectional view of the main part, whenthe reticle is held by the reticle holder.

[0049] The exposure apparatus 1 shown in FIG. 1 is schematicallyconstituted by an illumination optical system IU which illuminates arectangular (or circular-arc) illumination area on a reticle (sample,mask) R formed in a flat shape, with uniform illuminance by an exposureillumination light from a light source (not shown), a reticle holder 18for holding the reticle R, a stage apparatus 4 including a movablereticle stage (mask stage) 2 including the reticle holder 18 and areticle board 3 for supporting the reticle stage 2, a projection opticalsystem PL which projects illumination light emitted from the reticle Ronto a wafer (substrate, photosensitive substrate) W, a wafer holder(holding apparatus) 41 for holding the wafer W, a stage apparatus 7including a movable wafer stage (substrate stage) 5 including the waferholder 41 and a wafer board 6 for supporting the wafer stage 5, and abody 8 which supports the stage apparatus 4 and the projection opticalsystem PL. Here, a direction of the optical axis of the projectionoptical system PL is referred to as the Z direction, a synchronousmoving direction of the reticle R and the wafer W, being a directionorthogonal to the Z direction is referred to as the Y direction, and anasynchronous moving direction thereof is referred to as the X direction.A rotation direction about the respective axes is referred to as θZ, θY,and θx, respectively.

[0050] The illumination optical system IU is supported by a supportingcolumn 9, which is fixed on the upper face of the body 8. As theexposure illumination light, there can be used, for example, the brightlines (a g line, an h line, and an i line) in the ultraviolet regionemitted from a super-high pressure mercury lamp, far-ultraviolet light(DUV light) such as a KrF excimer laser beam (wavelength: 248 nm), andvacuum-ultraviolet light (VUV) such as an ArF excimer laser beam(wavelength: 193 nm) and an F₂ excimer laser beam (wavelength: 157 nm).

[0051] The body 8 is installed on a base plate 10 mounted horizontallyon the floor, and steps 8 a and 8 b protruding inwards are respectivelyformed on the upper side and the lower side thereof.

[0052] Of the stage apparatus 4, the reticle board 3 is supportedsubstantially horizontally on the steps 8 a in the body 8 via vibrationisolating units 11 at respective corners (the vibration isolating units11 on the other side on the page are not shown), and an opening 3 athrough which a pattern image formed on the reticle R passes is formedat the center thereof. A metal or alumina ceramics can be used for thematerial of the reticle board 3. The vibration isolating units 11respectively have a configuration such that an air mount 12 whose innerpressure is adjustable and a voice coil motor 13 are arranged on thestep 8 a in series. By these vibration isolating units 11, finevibrations transmitted to the reticle board 3 via the base plate 10 andthe body 8 are isolated at a micro G level (G is the acceleration ofgravity).

[0053] The reticle stage 2 is supported on the reticle board 3 so as tobe movable two-dimensionally along the reticle board 3. A plurality ofair bearings (gas bearings) 14 is fixed on the bottom face of thereticle stage 2, and the reticle stage 2 is floated and supported on thereticle board 3 by these air bearings 14 via a clearance of severalmicrons. An opening 2 a through which a pattern image of the reticle Rpasses, is formed at the center of the reticle stage 2, so as tocommunicate with the opening 3 a of the reticle board 3. The patternimage of the reticle R having passed through the openings 2 a and 3 aenters the projection optical system PL. As the projection opticalsystem PL, there is used a dioptric system having a 1/4 (or 1/5)reduction magnification and comprising dioptric elements (lens elements)using quartz or fluorite as an optical glass, in which both thesubstance surface (reticle R) side and the image surface (wafer W) sidehave a telecentric and circular projection field of view. Therefore,when the illumination light is irradiated onto the reticle R, of thecircuit pattern on the reticle R, an imaging beam from the portionilluminated by the illumination light enters the projection opticalsystem PL, and a partial inverted image of the circuit pattern isimaged, restricted in a slit form at the center of the circular field ofview on the image surface side of the projection optical system PL. As aresult, the partial inverted image of the projected circuit pattern istransferred in a reduced scale onto a resist layer on the surface of oneshot area, of a plurality of shot areas on the wafer W arranged on theimaging surface of the projection optical system PL.

[0054] A flange 23 integrally formed with a body tube is provided on theouter periphery of the body tube of the projection optical system PL.The projection optical system PL is inserted from above into the bodytube board 25 formed of a casting, which is supported substantiallyhorizontally via vibration isolating units 24 on the steps 8 b in thebody 8, setting the optical axis in the Z direction, with the flange 23engaging with the body tube board 25. For the body tube board 25,ceramics material having high rigidity and low thermal expansion may beused.

[0055] For the material of the flange 23, a material having low thermalexpansion, for example, Inver (an alloy having low expansion, comprisingiron containing nickel 36%, manganese 0.25%, a small amount of carbon,and other elements) is used. The flange 23 constitutes a so-calledkinematic support mount, which supports the projection optical system PLwith respect to the body tube board 25 at three points via a point, aplane and a V groove. Use of such a kinematic support mount providesadvantages in that assembly of the projection optical system PL withrespect to the body tube board 25 becomes easy, and a stress due tovibrations of the body tube board 25 and the projection optical systemPL after the assembly, and temperature changes can be reduced mosteffectively.

[0056] The vibration isolating units 24 are arranged at the respectivecorners of the body tube board 25 (the vibration isolating units 24 onthe other side on the page are not shown), and respectively have aconfiguration such that an air mount 26 whose inner pressure isadjustable and a voice coil motor 27 are arranged on the step 8 b inseries. By these vibration isolating units 24, fine vibrationstransmitted to the body tube board 25 (and the projection optical systemPL) via the base plate 10 and the body 8 are isolated at a micro Glevel.

[0057] The stage apparatus 7 is composed mainly of the wafer stage 5, awafer board 6 supporting the wafer stage 5 so as to be movabletwo-dimensionally along the XY plane, a sample support ST providedintegrally with the wafer stage 5 for attracting and holding the waferW, an X guide stage XG which supports the wafer stage 5 and the samplesupport ST relatively movably, and a synchronous stage apparatus whichmoves synchronously with the X guide stage XG. A plurality of airbearings (gas bearings) 28, being non-contact type bearings, is fixed onthe bottom face of the wafer stage 5, and the wafer stage 5 is floatedand supported on the wafer board 6 by these air bearings 28 via aclearance of several microns.

[0058] The wafer board 6 is supported substantially horizontally abovethe base plate 10 via vibration isolating units 29. The vibrationisolating units 29 are arranged at the respective corners of the waferboard 6 (the vibration isolating units 29 on the other side on the pageare not shown), and respectively have a configuration such that an airmount 30 whose inner pressure is adjustable and a voice coil motor 31are arranged on the base plate 10 in parallel. By these vibrationisolating units 29, fine vibrations transmitted to the wafer board 6 viathe base plate 10 are isolated at a micro G level.

[0059] The X guide stage XG has a shape having a long length along the Xdirection, and movable elements 36 constituting an armature unit arerespectively provided at the lengthwise opposite ends. Stators 37 havinga magnet unit corresponding to the movable elements 36 are provided onsupport portions 32 protruding from the base plate 10. These movableelements 36 and stators 37 constitute moving-coil type linear motors 33.The X guide stage XG moves in the Y direction, by driving the movableelements 36 by the electromagnetic interaction with the stators 37, andalso rotates and moves in the θZ direction by adjusting the drive of thelinear motors 33. In other words, the linear motors 33 drive the waferstage 5 (and the sample support ST, hereinafter simply referred to asthe wafer stage 5) in the Y direction and the θZ direction,substantially integrally with the X guide stage XG.

[0060] A movable element 34 a of an X trim motor 34 is attached to the−X direction side of the X guide stage XG. A stator 34 b of the X trimmotor 34 is provided on the body 8. Therefore, a reaction force at thetime of driving the wafer stage 5 in the X direction is transmitted tothe base plate 10 via the X trim motor 34 and the body 8.

[0061] The wafer stage 5 is supported and held in a non-contact mannerby the X guide stage XG, so as to be able to move relatively in the Xdirection, via a magnetic guide comprising a magnet and an actuator,which maintains a predetermined gap in the Z direction between the Xguide stage XG and the magnetic guide. The wafer stage 5 is driven inthe X direction by the electromagnetic interaction due to the X linearmotor 35 buried in the X guide stage XG. On the upper face of the waferstage 5, the wafer W is fixed by vacuum attraction or the like via thewafer holder 41.

[0062] In the stage apparatus 7, a sample support detection device fordetecting the position information of the sample support ST is arranged.The sample support detection device comprises an X movable mirror 43provided at the side edge of the sample support ST so as to be extendedalong the Y direction, and a laser interferometer (interferometer) 44arranged opposite to the X movable mirror 43. The laser interferometer44 irradiates laser beams (detection beams) toward the reflectingsurface of the X movable mirror 43 and a reference mirror 42 fixed atthe bottom of the body tube of the projection optical system PL, andmeasures a relative displacement between the X movable mirror 43 and thereference mirror 42, based on the interference between the reflectedlight and the incident light, to thereby detect the position of thesample support ST (and the wafer W) in the X direction at apredetermined resolution, for example, at a resolution of from about 0.5to 1 nm in real time. Similarly, though not shown in FIG. 1, there arealso provided a Y movable mirror provided at the side edge of the samplesupport ST so as to be extended along the X direction, and a Y laserinterferometer (interferometer) arranged opposite to the Y movablemirror with a gap in the X direction. The Y laser interferometerirradiates laser beams (detection beams) toward the reflecting surfaceof the Y movable mirror and a reference mirror (not shown) fixed at thebottom of the body tube of the projection optical system PL, andmeasures a relative displacement between the Y movable mirror and thereference mirror, based on the interference between the reflected lightand the incident light, to thereby detect the position of the samplesupport ST (and the wafer W) in the Y direction and the position(rotation about the Z axis) thereof in the θZ direction (about the axisorthogonal to the relative movement direction) at a predeterminedresolution, for example, at a resolution of from about 0.5 to 1 nm at areal time.

[0063] Three laser interferometers 45 are fixed at three differentpositions on the flange 23 of the projection optical system PL (however,only one laser interferometer is representatively shown in FIG. 1). Anopening 25 a is respectively formed in the portion of the body tubeboard 25, facing each laser interferometer 45, and laser beams (lengthmeasuring beams) in the Z direction are irradiated toward the waferboard 6 from the respective laser interferometers 45 via these openings25 a. Reflecting surfaces are respectively formed on the upper face ofthe wafer board 6, at positions facing each length measuring beam.Therefore, the Z position of the wafer board 6 at three different pointsis respectively measured based on the flange 23 by the three laserinterferometers 45 (however, in FIG. 1, since a shot area at the centerof the wafer W on the wafer stage 5 is in a state immediately below theoptical axis of the projection optical system PL, the length measuringbeam is interrupted by the wafer stage 5). Reflecting surfaces may beformed on the upper face of the sample support ST, and an interferometerfor measuring the Z-direction positions of the three different points onthe reflecting surfaces based on the projection optical system PL or theflange 23 may be provided.

[0064] The reticle stage 2 having the reticle holder 18 will now bedescribed in detail, with reference to FIG. 2 to FIG. 6.

[0065] As shown in FIG. 2 to FIG. 4, the reticle stage 2 comprises areticle coarse adjustment stage 16, and a reticle holder (holdingapparatus) 18 as a reticle fine adjustment stage provided on the reticlecoarse adjustment stage 16 (in FIG. 1, these are shown as one stage).

[0066] As shown in FIG. 2, a pair of Y linear motors (stage drive units)15 are connected to the reticle coarse adjustment stage 16, so that thereticle coarse adjustment stage 16 is driven by these Y linear motors 15on the reticle board 3, at a predetermined stroke in the Y-axisdirection. The respective Y linear motors 15 respectively comprise astator 20 supported so as to float on the reticle board 3 by a pluralityof air bearings 19, being non-contact type bearings, and a movableelement 21 provided corresponding to the stator 20 and fixed on thereticle coarse adjustment stage 16 via a connecting member 22.Therefore, in accordance with the law of conservation of momentum, thestator 20 moves in the −Y direction, corresponding to the movement ofthe reticle coarse adjustment stage 16 in the +Y direction. Due to themovement of the stator 20, a reaction force accompanying the movement ofthe reticle coarse adjustment stage 16 is compensated, and the positionof the center of gravity can be prevented from changing.

[0067] The stators 20 may be provided on the body 8, rather than on thereticle board 3. When the stators 20 are provided on the body 8, the airbearings 19 are omitted, and the stators 20 are fixed on the body 8, sothat the reaction force acting on the stators 20 due to the movement ofthe reticle coarse adjustment stage 16 may be removed to the floor viathe body 8.

[0068] The reticle coarse adjustment stage 16 is guided in the Y-axisdirection by a pair of Y guides 51 fixed on the upper face of an upperprotrusion 3 b formed at the center of the reticle board 3, andextending in the Y-axis direction. The reticle coarse adjustment stage16 is supported in a non-contact manner by air bearings (gas bearings)(not shown) with respect to these Y guides 51. The reticle coarseadjustment stage 16 and the Y guides 51 are formed of, for example, ametal or alumina ceramics.

[0069] As shown in FIG. 2 and FIG. 3, a pair of X voice coil motors 17Xand a pair of Y voice coil motors 17Y are provided on the reticle holder(reticle fine adjustment stage) 18. The reticle holder 18 is finelydriven in the X, Y and θZ directions on the reticle coarse adjustmentstage 16 by the voice coil motors, with the reticle holder 18 floatedwith respect to the upper face 16 a of the reticle coarse adjustmentstage 16 by the air bearings (not shown).

[0070] The reticle holder 18 is formed of ceramics, and particularly,formed of cordierite ceramics. Since this cordierite material has almostzero coefficient of thermal expansion, expansion of the reticle holder18 due to the heat generated by the actuators (voice coil motors) andthe like as the stage drive unit is suppressed. The reticle coarseadjustment stage 16 is also formed of ceramics, and cordierite or SiCceramics may be used. The reticle coarse adjustment stage 16 may beformed of a metal such as stainless steel.

[0071] A pair of Y movable mirrors 52 a and 52 b consisting of cornercubes is provided at the −Y direction end of the reticle holder 18, andan X movable mirror 53 consisting of a plane mirror extending in theY-axis direction is provided at the +X direction end of the reticleholder 18. Three laser interferometers (not shown) irradiate lengthmeasuring beams with respect to these movable mirrors 52 a, 52 b and 53to measure a distance from the respective movable mirrors, to therebymeasure the position of the reticle stage 2 in the X, Y and θZ (rotationabout the Z axis) directions with high accuracy. The positioninformation of the reticle stage 2 (the reticle holder 18 and thereticle coarse adjustment stage 16) measured by the laserinterferometers is output to a control unit, and the control unit drivesthe stage drive unit (the linear motor 15, and the voice coil motors 17Xand 17Y) so as to shift the reticle stage 2 to a predetermined position,based on the measurement result of the laser interferometers.

[0072] Similarly, the drive of the linear motors 33 and 35 for the waferstage 5 is also controlled by a control unit (not shown) in anintegrated manner.

[0073] As shown in FIG. 3, the reticle holder 18 comprises seat portions60 (60A, 60B and 60C) respectively provided at a plurality ofpredetermined positions so as to protrude in the Z direction, andsuction pads 62 respectively provided on the upper face of the seatportions 60. In this embodiment, three seat portions 60 and threesuction pads 62 are provided. As described above, an opening 2 a isprovided, through which the pattern image of the reticle R can pass, atthe center of the reticle holder 18. Similarly, an opening 2 a isprovided at the center of the reticle coarse adjustment stage 16.

[0074] As shown in FIG. 4 and FIG. 5, the respective suction pads 62provided on the seat portions 60 comprise an annular groove 61 formed soas to extend in the Y direction, a boundary portion 65 formed inside ofthe annular groove 61, and a first pore (first suction device) 70 a anda second pore (second suction device) 70 b communicates with the annulargroove 61. As shown in FIG. 4, the respective pores 70 a and 70 b areconnected to a compressor (suction apparatus) 72 via suction paths 71.The pore 70 a is arranged in a first suction section (first holdingsection) 63 of the annular groove 61, which is a linear portion on theopening 2 a side, and the pore 70 b is arranged in a second suctionsection (second holding section) 64 of the annular groove 61, which is alinear portion on the opposite side of the opening 2 a (see the hashedportion in FIG. 5A, for the first suction section 63 and the secondsuction section 64). In other words, the respective first suctionsection 63 and second suction section 64 are arranged respectively in aplurality of positions (three places) with respect to the lower face Raof the reticle R, and the first suction section 63 and the secondsuction section 64 are arranged adjacent to each other, with theboundary portion 65 placed therebetween.

[0075] Valves 71 a capable of adjusting the suction quantity of a gasper unit time, which is sucked from the pores 70 a and 70 b, arerespectively provided in the respective suction paths 71. The operationof the valves 71 a is separately controlled by a control unit CONT,respectively. In other words, the control unit CONT can control thesuction quantity of the gas per unit time by the first pore 70 a, andthe suction quantity of the gas per unit time by the second pore 70 b,respectively and separately. In FIG. 4, only the suction pads 62provided on the seat portions 60A and 60B are shown, but the suction padprovided on the seat portion 60C has a similar configuration.

[0076] As shown in FIG. 3, FIG. 5B and FIG. 6, the reticle R has apellicle PE for protecting a pattern area PA where a pattern is formedin the central part of the lower face (surface to be attracted) Ra. Theseat portions 60 of the reticle holder 18 hold a holdable area CA, beingportions other than the portion where the pellicle PE is provided, onthe lower face of the reticle R. The reticle R has a precisionwarrantable area (first area) AR1 including the pattern area PA andhaving a predetermined surface precision, and a precision unwarrantablearea AR2 other than the precision warrantable area AR1 of the lower faceRa. In other words, on the lower face Ra of the reticle R, the wholesurface is not necessarily processed so as to have the predeterminedsurface precision, and the predetermined surface precision is notwarranted on the outer rim portion.

[0077] As shown in FIG. 5B and FIG. 6, on the lower face Ra of thereticle R, the central part is a planar portion, and outsides of thecentral part are tapered portions formed in a direction away from theseat portion 60 outwards from the central side. The planar portionformed in the central part on the lower face of the reticle R becomesthe precision warrantable area AR1, and the tapered portions are theprecision unwarrantable area AR2. The tapered shape of the reticle R canbe formed by grinding the outer rim on the lower face Ra of the reticleR by a grinding device. When the holdable area CA of the reticle R ismounted on the seat portions 60, the first suction section 63 in thesuction pad 62 is set so as to be arranged opposite to the precisionwarrantable area AR1, of the lower face Ra of the reticle R. Moreover,the second suction section 64 in the suction pad 62 is set so as to bearranged opposite to the precision unwarrantable area AR2, of the lowerface Ra of the reticle R. The suction apparatus 72 draws out the gas inthe space between the precision warrantable area AR1 on the lower faceRa of the reticle R and the first suction section 63 via the pore (firstsuction device) 70 a, and draws out the gas in the space between theprecision unwarrantable area AR2 on the lower face Ra of the reticle Rand the second suction section 64 via the pore (second suction device)70 b.

[0078] At this time, as shown in FIG. 6, the boundary portion 65 betweenthe adjacent first suction section 63 and second suction section 64 isset to be arranged in the precision warrantable area AR1, on the lowerface Ra of the reticle R.

[0079] It has been described above that the gas in the space between theprecision warrantable area AR1 and the first suction section 63, and thegas in the space between the precision unwarrantable area AR2 and thesecond suction section 64 are drawn out via the pore 70 a and the pore70 b, respectively and separately. However, in this embodiment, sincethe first suction section 63 and the second suction section 64 areconnected to each other, the gas drawn out via the pore 70 a includes apart of the gas in the space between the precision unwarrantable areaAR2 and the second suction section 64, and the gas drawn out via thepore 70 b includes a part of the gas in the space between the precisionwarrantable area AR1 and the first suction section 63.

[0080] As shown in FIG. 6, the upper end face of the first suctionsection 63 and the upper end face of the second suction section 64 areformed to be the same height. That is, the upper face of the suction pad62 is flush.

[0081] The first suction section 63 and the planar precision warrantablearea AR1 come in contact with each other, but there is a predeterminedgap H between the second suction section 64 and the tapered precisionunwarrantable area AR2. In other words, though the suction quantity ofthe gas per unit time from the first pore 70 a and the suction quantityof the gas per unit time from the second pore 70 b are set to be thesame value, by providing the gap H, the area on the lower face Ra of thereticle R to be attracted by the first suction section 63 becomes largerthan the area attracted by the second suction section 64. In otherwords, if it is assumed that the length thereof in the directionperpendicular to the page in FIG. 6 is the same, RaA becomes larger thanRaB. As a result, the attraction of the second suction section 64 withrespect to the reticle R becomes weaker than that of the first suctionsection 63 with respect to the reticle R. This gap H is set such thatthe reticle R is not distorted due to the precision unwarrantable areaAR2 being attracted by the second suction section 64, and such that thesecond suction section 64 and the first suction section 63 can stablyhold the reticle R.

[0082] A method for holding the reticle R by the reticle holder 18having the above described configuration will now be described.

[0083] A predetermined reticle R is loaded on the reticle holder 18 by areticle carrier device (not shown). When the reticle R is loaded withrespect to the reticle holder 18, loading is performed while performingalignment such that of the holdable area CA of the reticle R, theprecision warrantable area AR1 faces the first suction section 63 andthe precision unwarrantable area AR2 faces the second suction section64. At this time, alignment is performed such that of the suction pad62, the boundary portion 65 between the first suction section 63 and thesecond suction section 64 is arranged at least in the precisionwarrantable area AR1.

[0084] When the reticle R has been loaded on the reticle holder 18, thecontrol unit CONT drives the suction apparatus 72, and controls thevalves 71 a respectively provided in the suction path 71, to set thesuction quantity of the gas per unit time by the first pore 70 a and thesuction quantity of the gas per unit time by the second pore 70 b to aset value set beforehand. In this embodiment, the control unit CONT setsthe suction quantity of the gas per unit time by the first pore 70 a andthe suction quantity of the gas per unit time by the second pore 70 b tothe same value.

[0085] The reticle R is attracted and held such that the precisionwarrantable area AR1 and the precision unwarrantable area AR2 arerespectively attracted by the first suction section 63 and the secondsuction section 64. Since a wide range of the holdable area CA of thereticle R is held by using the first suction section 63 and the secondsuction section 64, the reticle R is stably held by the reticle holder18, and even if the reticle stage 2 moves at high speed, the reticle Ris not shifted from the reticle holder 18 due to inertia force.

[0086] Moreover, since the precision warrantable area AR1 of the reticleR is held by the first suction section 63, and the precisionunwarrantable area AR2 is held by the second suction section 64,separately, the reticle holder 18 can hold the reticle R stably withoutdeforming the reticle R. In other words, since the precisionunwarrantable area AR2 of the reticle R is formed in a tapered shape, toprovide a gap H between the second suction section 64 and the precisionunwarrantable area AR2, the area on the lower face Ra of the reticle Rattracted by the first suction section 63 becomes larger than the areaattracted by the second suction section 64, and hence attraction of thesecond suction section 64 with respect to the reticle R is set to beweaker than that of the first suction section 63 with respect to thereticle R. Therefore, at the time of attracting and holding theprecision unwarrantable area AR2, distortion of the whole reticle Rresulting from the precision unwarrantable area AR2 being attracted andheld can be suppressed.

[0087] At this time, the leak quantity from the gap H (that is, the gapH) is set such that the reticle R is not distorted, and the stableholding power with respect to the reticle R does not drop. In otherwords, the leak quantity from the gap H is set such that even if thereticle stage 2 moves at high speed, the reticle R is not shifted fromthe reticle holder 18 due to the inertia force. The pattern formed onthe reticle R can be exposed on the wafer W with high accuracy via theprojection optical system PL, by irradiating the exposure light from theillumination optical system IU onto the reticle R held by the reticleholder 18.

[0088] The reason why the reticle holder 18 can hold the reticle Rwithout any deformation by holding the precision warrantable area AR1 ofthe reticle R by the first suction section 63 and holding the precisionunwarrantable area AR2 by the second suction section 64 will bedescribed below, with reference to FIGS. 7A to 7D, FIG. 8 and FIG. 9.FIGS. 7A to 7D are schematic diagrams in which simulation results of theshape (deformation) of the reticle R are shown, when the tapered area ofthe reticle R, that is, the size L of the precision unwarrantable areaAR2 of the reticle R is set to different values, and the reticle R isattracted and held by the first suction section 63 and the secondsuction section 64, respectively. FIGS. 7A to 7D are diagrams when thesize L of the precision unwarrantable area is set to 5.5 mm, 7.5 mm, 9.0mm, and 10.5 mm, respectively. In the respective figures of FIGS. 7A to7D, the maximum value H of the gap between the second suction section 63and the precision unwarrantable area AR2 is set to the same value (0.5μm), and the same reticle holder 18 (suction pad 62) is used.

[0089]FIG. 7A illustrates the simulation result, when the size L of theprecision unwarrantable area AR2 is set to 5.5 mm. In this figure, theprecision warrantable area AR1 is held by the first suction section 63,and the precision unwarrantable area AR2 is held by the second suctionsection 64. At this time, the boundary portion 65 between the firstsuction section 63 and the second suction section 64 is arranged in theprecision warrantable area AR1.

[0090] In this state, when the reticle R is attracted by the firstsuction section 63 and the second suction section 64, as shown in FIG.7A, moments M1 and M2 about a point C are generated. This point C is apoint on the precision warrantable area AR1. As described above, at thistime, the attraction by the second suction section 64 with respect tothe precision unwarrantable area AR2 becomes weaker than that by thefirst suction section 63 with respect to the precision warrantable areaAR1 due to the gap H, and the area of the first suction section 63 withrespect to the precision warrantable area AR1 is larger than the area ofsecond suction section 64 with respect to the precision unwarrantablearea AR2. As a result, M1 is larger than M2, and hence a force thatallows the precision warrantable area AR1 to peel off from the firstsuction section 63 is not generated with respect to the reticle R.

[0091] Therefore, in this state, the reticle R is held by the reticleholder 18 stably.

[0092]FIG. 7B illustrates the simulation result, when the size L of theprecision unwarrantable area AR2 is set to 7.5 mm. In this figure, theprecision warrantable area AR1 is held by the first suction section 63,and the precision unwarrantable area AR2 is held by the second suctionsection 64. At this time, the boundary portion 65 between the firstsuction section 63 and the second suction section 64 is arranged in theprecision unwarrantable area AR2.

[0093] In this state, when the reticle R is attracted by the firstsuction section 63 and the second suction section 64, as shown in FIG.7B, moments M3 and M4 about the point C are generated. In this case, thearea of the first suction section 63 with respect to the precisionwarrantable area AR1 is smaller than the area of second suction section64 with respect to the precision unwarrantable area AR2, and theattraction by the second suction section 64 with respect to theprecision unwarrantable area AR2 becomes stronger than that by the firstsuction section 63 with respect to the precision warrantable area AR1.As a result, M4 is larger than M3. Then, a force that allows theprecision warrantable area AR1 to peel off from the first suctionsection 63 acts on the reticle R, and as shown by the broken line R′,the reticle R deforms so as to raise the central portion (pattern area).Therefore, since the precision warrantable area AR1 including thepattern area also distorts, it is not desired to set the area of thefirst suction section 63 with respect to the precision warrantable areaAR1 to be smaller than the area of second suction section 64 withrespect to the precision unwarrantable area AR2.

[0094] In this case, if it is assumed that the seat portion in FIG. 7Bis 60A (or 60B), attraction operation with respect to the reticle R isconducted by the first suction section 63 and the second suction section64 in the seat portion 60C on the opposite side. Therefore, a reactionforce M3′ against bending acts on the reticle R, as shown in FIG. 7B.Moreover, since the center C of the moment exists on the boundaryportion 65, moments about the point C are balanced, so that the firstsuction section 63 and the precision warrantable area AR1 do not peeloff from each other.

[0095]FIG. 7C illustrates the simulation result, when the size L of theprecision unwarrantable area AR2 is set to 9.0 mm. In this figure, theprecision warrantable area AR1 and a part of the precision unwarrantablearea AR2 are held by the first suction section 63, and the precisionunwarrantable area AR2 is held by the second suction section 64. At thistime, the boundary portion 65 between the first suction section 63 andthe second suction section 64 is arranged completely in the precisionunwarrantable area AR2.

[0096] In this state, when the reticle R is attracted by the firstsuction section 63 and the second suction section 64, as shown in FIG.7C, a moment M5 about the point C is generated. In this case, the areaof the first suction section 63 with respect to the precisionwarrantable area AR1 is smaller than the area of second suction section64 with respect to the precision unwarrantable area AR2. In this case,the reticle R deforms so as to raise the central portion (pattern area),as shown by the broken line R′, and the first suction section 63 and theprecision warrantable area AR1 peel off from each other completely. Ifit is assumed that the seat portion in FIG. 7C is 60A (or 60B), areaction force M5′ against bending acts on the reticle R, as shown inFIG. 7C, due to the attraction operation with respect to the reticle Rby the first suction section 63 and the second suction section 64 in theseat portion 60C on the opposite side. The deformation of the reticle Rfinishes at a point in time when the deformation of the reticle Rprogresses so that a point C1 of the reticle R comes in contact with theboundary portion 65, and the moment about this point C1 is balanced withthe reaction force M5′.

[0097]FIG. 7D illustrates the simulation result, when the size L of theprecision unwarrantable area AR2 is set to 10.5 mm. In this figure, theprecision warrantable area AR1 is neither held by the first suctionsection 63 nor the second suction section 64, and the precisionunwarrantable area AR2 is held by the first suction section 63 and thesecond suction section 64. The boundary portion 65 between the firstsuction section 63 and the second suction section 64 is arranged in theprecision unwarrantable area AR2.

[0098] In this state, when the reticle R is attracted by the firstsuction section 63 and the second suction section 64, as shown in FIG.7D, a moment M6 about the point C is generated. In this case, the areaof the first suction section 63 with respect to the precisionwarrantable area AR1 is almost zero. The reticle R deforms so as toraise the central portion (pattern area), as shown by the broken lineR′, and the first suction section 63 and the precision warrantable areaAR1 peel off from each other completely.

[0099] The deformation of the reticle R finishes at a point in time whenthe precision unwarrantable area AR2 comes in contact with the firstsuction section 63 and the second suction section 64, as shown by thebroken line R′.

[0100] As described above, as in the state shown by FIG. 7A, by settingthe size L to not larger than 5.5 mm, so that the boundary portion 65between the first suction section 63 and the second suction section 64is arranged in the precision warrantable area AR1, and the area of thefirst suction section 63 with respect to the precision warrantable areaAR1 is larger than the area of second suction section 64 with respect tothe precision unwarrantable area AR2, occurrence of peeling between thefirst suction section 63 and the precision warrantable area AR1 can besuppressed, and distortion of the reticle R can be prevented.

[0101]FIG. 8 shows simulation results at the time of obtaining themaximum deflection of the reticle R, when the size L of the precisionunwarrantable area AR2 and the maximum gap H between the second suctionsection 64 and the precision unwarrantable area AR2 are respectivelychanged. FIG. 9 is obtained by changing the table in FIG. 8 to agraphical representation, wherein the maximum deflection of the reticleR is plotted on the Y axis, and the size L of the precisionunwarrantable area AR2 is plotted on the X axis. Here, the maximumdeflection of the reticle R stands for a distance in the Z directionbetween the end portion and the central portion of the reticle R, whenthe reticle R deforms to raise the central portion.

[0102] From these figures, it is seen that the maximum deflection of thereticle R increases rapidly, when the size L is 2.5 mm, 5.5 mm and 7.5mm. From this result, it has been found that the deformation of thereticle R largely depends on the size L of the precision unwarrantablearea AR2, that is, whether the precision unwarrantable area AR2 isattracted by the first suction section 63.

[0103] Next is a description of another embodiment of the holdingapparatus of the present invention. In the following description withreference to the drawings, components the same as or equivalent to thosein the above described embodiment are denoted by the same referencesymbols, and the description thereof is simplified or omitted.

[0104] The shape of the precision unwarrantable area AR2 of the reticleR is not limited to the tapered shape, provided this is setcorresponding to the shape of the second suction section 64 whichattracts and holds the precision unwarrantable area AR2 of the reticleR, so as to have a predetermined gap H between the second suctionsection 64 and the precision unwarrantable area AR2 of the reticle R.For example, as shown in FIG. 10, the precision unwarrantable area AR2may be a step formed in a direction away from the second suction section64.

[0105] In this embodiment, the construction is such that the poresconnected to the suction apparatus 72 via the suction path 71 arerespectively provided in the first suction section 63 and the secondsuction section 64, being linear portions of the annular groove 61formed in the suction pad 62 so as to extend in the Y direction.However, as shown in FIG. 11, the pore provided in the annular groove 63may be only one. In this case, since the first suction section 63 andthe second suction section 64 are a part of the annular groove 61, andare continuous, then even if the pore 70 is only one, the suctionoperation can be stably performed. Moreover, the pores 70 may beprovided at a plurality of optional positions, respectively, in theannular groove 61. In this case, the suction path 71 is connected toeach of the plurality of pores, to perform the suction operation by thesuction apparatus 72.

[0106] In this embodiment, the suction quantity of the gas per unit timefrom the first pore 70 a and the suction quantity of the gas per unittime from the second pore 70 b are set to be the same value, but therespective suction quantity may be set to different values. In thiscase, as shown in FIG. 4, the control unit CONT controls the valves 71 arespectively provided in a plurality of connecting paths 71,respectively and separately. Alternatively, other than the control bythe valves 71 a, the suction apparatus 72 may be provided respectivelyseparately with respect to each of the suction paths 71, so that thecontrol unit CONT controls the respective outputs of the suctionapparatus 72 separately.

[0107] In this embodiment, by providing the gap H between the secondsuction section 64 and the precision unwarrantable area AR2, theattraction by the second suction section 64 with respect to theprecision unwarrantable area AR2 is set to be weaker than that by thefirst suction section 63 with respect to the precision warrantable areaAR1. However, the attraction by the second suction section 64 withrespect to the precision unwarrantable area AR2 may be set to becomeweaker than that by the first suction section 63 with respect to theprecision warrantable area AR1, by setting such that the suctionquantity of the gas per unit time from the first pore 70 a is largerthan the suction quantity of the gas per unit time from the second pore70 b.

[0108] In this embodiment, the respective linear portions of the annulargroove 61 formed in the suction pad 62 so as to extend in the Ydirection, are designated as the first suction section 63 and the secondsuction section 64. However, as shown in FIG. 12, the first suctionsection 63 and the second suction section 64 may be provided in thesuction pad 62, respectively and separately. Then, the pore 70 isrespectively provided for the first suction section 63 and the secondsuction section 64, and by connecting the first suction section 63 andthe second suction section 64 separately to the suction apparatus 72,the suction operation by the first suction section 63 and the secondsuction section 64 becomes possible. In this case, by separatelycontrolling the outputs of the respective suction apparatus 72, theattraction by the first suction section 63 with respect to the precisionwarrantable area AR1 and the attraction by the second suction section 64with respect to the precision unwarrantable area AR2 can be controlledrespectively and separately.

[0109] In this embodiment, the height position of the first suctionsection 63 and that of the second suction section 64 are set to be thesame, but as shown in FIG. 13A. the height position thereof may be setsuch that the second suction section 64 is at a lower position withrespect to the lower face Ra of the reticle R than the first suctionsection 63. By having such a construction, a predetermined gap H can beformed between the second suction section 64 and the precisionunwarrantable area AR2 of the reticle R, even if the tapered 10 portionis not formed in the reticle R.

[0110] On the other hand, as shown in FIG. 13B, the height position ofthe second suction section 64 may be set at a higher position withrespect to the lower face Ra of the reticle R than the first suctionsection 63. By having such a construction, a predetermined gap H canstill be formed between the second suction section 64 and the precisionunwarrantable area AR2 of the reticle R, even if the precisionunwarrantable area AR2 of the reticle R is formed in a direction tolargely separate this from the suction pad 62.

[0111] In other words, the height position of the second suction section64 is set according to the shape of the lower face Ra of the reticle R.

[0112] Moreover, a seat portion where the first suction section 63 isprovided, and a seat portion where the second suction section 64 isprovided may be provided independently, and either one of the two seatportions may be supported by a supporting apparatus movable in the Zdirection so that the seat portion which is supported movably is movedin the Z direction to thereby control the height position of the firstsuction section 63 or the second suction section 64. At this time, therespective seat portions may be arranged side by side in the Xdirection, or may be arranged away from each other in the Y direction.

[0113] Furthermore, the respective seat portions 60A, 60B and 60C shownin FIG. 3 may be supported by a supporting apparatus movable in adirection approaching or separating from the opening 2 a (that is, inthe X direction), and the seat portions may be moved so that the secondsuction sections 64 provided in the respective seat portions hold theprecision unwarrantable area AR2, corresponding to the size L of theprecision unwarrantable area AR2 of the reticle R to be mounted.

[0114] It is not necessary to make the sizes of the first suctionsection 63 and the second suction section 64 the same, and these mayhave a different size (area). For example, the width (the size in the Xdirection) of the second suction section 64 may be set to be smallerthan the width (the size in the X direction) of the first suctionsection 63. Alternatively, as shown in FIG. 14, the sizes in the Ydirection of the first suction section 63 and the second suction section64 may be set to be different from each other. The respective suctionpads 62 shown in FIG. 14 comprise one first holding section 63, andthree second holding sections 64 smaller than the first holding section63. In this case, the total of the respective sizes (areas) of the threesecond holding sections 64 is set to be smaller than the size (area) ofthe first holding section 63. The upper face of a seat portion 60 whichdoes not have the suction function is exposed between the second holdingportions 64. By having such a construction, the attraction of the secondsuction section 64 with respect to the precision unwarrantable area AR2can be set to be smaller than that of the first suction section 63 withrespect to the precision warrantable area AR1, and hence the reticleholder 18 can stably hold the reticle R without any distortion.

[0115] In this embodiment, three seat portions having the suction pad 62are provided, but the seat portion having the suction pad 62 may beprovided in a plurality of optional positions. Moreover, in thisembodiment, each of the suction pads 62 has the first suction section 63and the second suction section 64, but the construction may be suchthat, of the suction pads 62 provided in the plurality of seat portions,only the first suction section 63 is provided and the second suctionsection 64 is not provided in some suction pads.

[0116] When a plurality of seat portions 60 having the suction pad 62 isprovided, it is not necessary to perform the attraction operation withrespect to the reticle R by all the suction pads 62. For example, of thesuction pads 62 provided in a plurality of places, some of the optionalsuction pads 62 may be used to perform the attraction operation withrespect to the reticle R, and the other suction pads 62 need not performthe attraction operation. In other words, the construction may be suchthat the attraction operation by the suction pads 62 provided in aplurality of places can be switched.

[0117] The suction quantity of the gas per unit time from the secondpore 70 b provided in the second suction section 64 (that is, theattraction of the second suction section 64 with respect to theprecision unwarrantable area AR2), or the suction position of the secondsuction section 64 with respect to the reticle R may be setcorresponding to the shape (degree of deformation) of the reticle R. Inother words, the suction quantity of the gas per unit time from thesecond pore 70 b is controlled, or when the second suction section 64 ismovably provided, the position thereof is controlled, so that thereticle R held by the reticle holder 18 becomes flat, in order toperform the exposure processing with high accuracy.

[0118] Setting of the suction quantity of the gas per unit time from thesecond pore 70 b, and setting of the position of the second suctionsection 64 may be performed, for example, by measuring the shape(deformation quantity) of the reticle R by a shape measuring device (anoptical shape sensor or the like), so that the shape of the reticle Rbecomes a desired shape based on the measurement result.

[0119] In this embodiment, the tapered portion of the reticle R isdesignated as the precision unwarrantable area AR2, but a part of thetapered portion may include the precision warrantable area.

[0120] When the attraction holding power with respect to reticle R bythe reticle holder 18 is not sufficient, the holding power can beimproved by pressing downward from above a portion on the upper face ofthe reticle R corresponding to the position held by the reticle holder18, for example, by a predetermined pressing apparatus.

[0121] In this embodiment, a gap H is provided between the secondholding section 64 and the precision unwarrantable area AR2 of thereticle R, but since this gap H is for example about 5 μm, the secondholding section 64 can perform the attraction operation with respect tothe reticle R due to the viscosity of the gas (air).

[0122] In this embodiment, the holding apparatus of the presentinvention is applied to the reticle holder, but it is also applicable tothe wafer holder 41 for holding the wafer W.

[0123] The holding apparatus of the present invention is also applicableto apparatus other than the exposure apparatus, for example, surveyinstruments or apparatus for forming a circuit pattern on a reticle.

[0124] The substrate in this embodiment is applicable not only to thesemiconductor wafer W for semiconductor devices, but also to a glasssubstrate for liquid crystal display devices and a ceramic wafer forthin film magnetic heads.

[0125] The exposure apparatus 1 is also applicable to a projectionexposure apparatus of a step and repeat type (stepper) wherein a patternof the reticle R is exposed in a state with the reticle R and the waferW stationary, and the wafer W is sequentially shifted step by step, inaddition to a scanning exposure apparatus of a step and scan type(scanning stepper; U.S. Pat. No. 5,473,410) wherein a pattern of thereticle R is scanned and exposed, while the reticle R and the wafer aresynchronously moved.

[0126] The kinds of the exposure apparatus 1 are not limited to theexposure apparatus for manufacturing semiconductor devices wherein asemiconductor device pattern is exposed on the wafer W, and for example,the exposure apparatus is widely applicable to exposure apparatus formanufacturing liquid crystal display elements, or exposure apparatus formanufacturing thin film magnetic heads, image-sensing devices (CCD) orreticles.

[0127] For the light source for the exposure illumination light, notonly bright lines (a g line (436 nm), an h line (404.7 nm), and an iline (365 nm)) emitted from a super-high pressure mercury lamp, a KrFexcimer laser (248 nm), an ArF excimer laser (193 nm) and an F₂ excimerlaser (157 nm), but also an X-ray or charged particle beams such aselectron beams may be used. For example, when the electron beam is used,thermionic emission type lanthanum hexaboride (LaB₆) and tantalum (Ta)may be used as an electron gun. 10 Moreover, when the electron beam isused, the reticle R may be used, or the reticle R not used and a patternmay be formed directly on the wafer. Furthermore, high frequency such asa YAG laser or a semiconductor laser may be used.

[0128] The magnification of the projection optical system PL may involvenot only a reduction system but may also involve an equal magnificationor enlarging system. As the projection optical system PL, when afar-ultraviolet ray such as an excimer laser is used, a material whichtransmits the far-ultraviolet ray, such as quartz or fluorite, is usedas the glass material, and when an F₂ laser or X-ray is used, areflection/refraction system or a refraction system is used as theoptical system (also for the reticle, one of a reflection type is used),or when an electron beam is used, an electronic optical systemconsisting of an electron lens and a deflector may be used as theoptical system. Here, needless to say, the optical path along which theelectron beam passes is evacuated. The invention is also applicable to aproximity exposure apparatus wherein the projection optical system PL isnot used, and the reticle R and the wafer are brought into close contactwith each other, to expose a pattern of the reticle R.

[0129] When a linear motor is used for the wafer stage 5 and the reticlestage 2 (see U.S. Pat. No. 5,623,853 or U.S. Pat. No. 5,528,118), eitherof an air floating type using an air bearing or a magnetic floating typeusing Lorentz force or reactance force may be used. Moreover, therespective stages 2 and 5 may be of a type which moves along a guide, ora guideless type without a guide.

[0130] As the drive for the respective stages 2 and 5, a planar motormay be used wherein a magnetic unit in which magnets are arrangedtwo-dimensionally (permanent magnet) and an armature unit in which coilsare arranged two-dimensionally are made to face each other, and therespective stages 2 and 5 are driven by an electromagnetic force. Inthis case, either the magnetic unit or the armature unit may beconnected to the stages 2 and 5, and the other of the magnetic unit andthe armature unit may be provided on the moving plane side (base) of thestages 2 and 5.

[0131] As described above, the exposure apparatus 1 of the embodiment ofthis application is manufactured by assembling various sub-systemsincluding respective constituents mentioned in the claims of thisapplication, so as to maintain a predetermined mechanical precision,electrical precision and optical precision. To ensure these variousprecisions, there are performed adjustment for obtaining the opticalprecision with respect to various optical systems, adjustments forobtaining the mechanical precision with respect to various mechanicalsystems and adjustments for obtaining the electrical precision withrespect to various electric systems, before and after assembly. Theassembly process from various sub-systems to the exposure apparatusincludes mechanical connection, wiring connection of electric circuitsand piping connection of pneumatic circuits between various sub-systems.Prior to the assembly process from the various sub-systems to theexposure apparatus, there is, of course, an assembly process of eachsub-system. After the assembly process from the various sub-systems tothe exposure apparatus has been completed, comprehensive adjustment isperformed, to thereby ensure various precisions for the overall exposureapparatus. In addition, it is desirable that the production of theexposure apparatus be performed in a clean room wherein the temperature,the degree of cleanness and the like are controlled.

[0132] A semiconductor device is manufactured, as shown in FIG. 25,through steps such as a step 201 for designing the function andperformance of the device, a step 202 for producing masks (reticles)based on the designing step, a step 203 for producing wafers from asilicon material, a substrate processing step 204 for exposing a patternof a reticle on a wafer by means of the exposure apparatus in the abovedescribed embodiment, a device assembly step (including dicing step,bonding step and packaging step) 205, and an inspection step 206.

[0133] [Second Embodiment]

[0134]FIG. 15 to FIG. 21 illustrate a second embodiment of the presentinvention. This embodiment has a feature in that a so-called pin andchuck holder is used as a reticle holder 90. Other configuration of theapparatus is the same as that of the first embodiment described above.

[0135]FIG. 15 is a perspective view of the reticle holder 90. Arectangular opening 2 a is formed at the center of the reticle holder90, and suction pads 91 having a long and slender rectangular shape areformed on the opposite sides of the opening 2 a on the upper face of thereticle holder 90, each aligned along the side of the opening 2 a.

[0136] These suction pads 91 have, respectively, a partition wall 92which surrounds a rectangular decompression area 95 for maintaining thedegree of vacuum, a plurality of pins 96 formed in the decompressionarea 95, with intervals therebetween, and exhaust holes 94 which openinto the decompression area 95. The width and height of the partitionwall 92 are constant over the whole periphery, and the upper end facesof the partition wall 92 and the pins 96 are polished from the upperface of the holder, so as to have the same height precisely. An error inthe height of the partition wall 92 and the pins 96 can be generallysuppressed to 50 nm or below. Ceramics is the most suitable material forthe reticle holder 90. The exhaust holes 94 are connected to a vacuumline (not shown), so as to be able to exhaust the gas in thedecompression area 95.

[0137]FIG. 16 shows the reticle R attracted by the reticle holder 90,and the contact portion between the reticle R and the suction pads isshown by hatching.

[0138] When such a reticle holder 90 is used, the same effects as thoseof the above described embodiment can be obtained. This point will bedescribed with reference to FIG. 17 to FIG. 21.

[0139]FIG. 17 is an enlarged sectional view illustrating a case where areticle R whose end is not tapered is attracted by the reticle holder90, wherein the upper end face (attracting face) of the partition wall92 is arranged at a position of from 1 to 2.5 mm and from 10.5 to 12 mmfrom the edge of the reticle R, to form a sealing portion.

[0140]FIG. 18 shows a case where the outside of the position of 5.5 mmfrom the edge of the reticle R is tapered, as an embodiment of thepresent invention. The center between the partition walls 92 of therespective suction pads 91 in the reticle holder 90 is located at aposition of 6.5 mm from the edge of the reticle R. In this case, astarting point P1 of the taper is located outside of the center betweenthe partition walls 92 of the respective suction pads 91 in the reticleholder 90. Therefore, a moment M2 about a point P1 generated due todecompression in the decompression area 95 is larger than a moment M1 inthe other direction, and hence a moment which causes peeling of theportion G further inside the reticle than the point P1, from the suctionpad 91 is not generated.

[0141] On the other hand, as shown in FIG. 19, when a taper startingpoint P2 of the reticle R is set to a position of 7.5 mm from the edgeof the reticle, a moment M4 about a point P1 generated due todecompression in the decompression area 95 becomes smaller than a momentM3 in the other direction, and hence a moment which causes peeling ofthe portion G further inside the reticle than the point P1, from thesuction pad 91 is generated. However, since the other end of the reticleR is attracted by the other suction pad 91, a bending moment works onthe reticle R, and a counter moment M41 against this bending moment isgenerated. As a result, the moments M41, M4 and M3 are balanced, and thereticle R is distorted.

[0142] As shown in FIG. 20, when a taper starting point P3 of thereticle R is set to a position of 9 mm from the edge of the reticle, themoment M3 in a direction distorting the reticle R further increases, andas shown in FIG. 21, when a taper starting point P4 is located on theupper end face of the inside partition wall 92, the distorted quantityof the reticle R becomes largest.

[0143] As described above, in the second embodiment, since the pin andchuck type reticle holder 90 is used, the taper starting point of thereticle R needs only to be outside of the center in the width directionof the suction pad 91, as with the taper starting point P1 shown in FIG.18. For example, when the center between the partition walls 92 of therespective suction pads 91 in the reticle holder 90 is located at aposition of 6.5 nm from the edge of the reticle R, the deformation ofthe attracted reticle can be kept to a minimum, by combining with areticle with the taper starting from outside of the position of 6 mmfrom the edge.

[0144] Moreover, since a plurality of pins 96 comes in contact with thereticle, there is the effect of increasing a static frictional forcebetween the reticle holder 90 and the reticle.

[0145] [Third Embodiment]

[0146] In the present invention, by placing a reticle R with the end ofthe reticle R being curved, as shown in FIG. 23 and FIG. 24, instead offorming the tapered portion at the end of the reticle R, a similareffect can be obtained. This point will be described below.

[0147] As shown in FIG. 22, when a stress P is applied perpendicularlyto the upper face of the reticle, at the opposite ends of a flat reticleR having a uniform thickness, at a position of distance x from one endof the reticle R, a stress, a shearing force, a bending moment andflexure expressed by the following equations occur, where l₁ denotes aninterval between a central supporting point and an outside supportingpoint of the reticle R in the attraction holding section (firstattraction holding section) of the reticle holder, l₂ denotes aninterval between the central supporting points in the respectiveattraction holding sections, 6 denotes an interval (gap) between theoutside supporting point and the reticle R, which is generated when thereticle R is mounted on the central supporting point, P denotes aproduct of the atmospheric pressure and an attraction area of theattraction holding section, E denotes a modulus of longitudinalelasticity of the reticle R, and I denotes a geometrical moment ofinertia of the reticle R.

[0148] (Reaction force: R₁, R₂)

R ₁ =R ₂ =P

[0149] (Shearing force: Q)

[0150] When 0<x<l₁, Q=−P₁

[0151] When l<x<l₁+l₂, Q=0

[0152] When l₁+l₂<x<2l₁+l₂, Q=P,

[0153] (Bending moment: M)

[0154] When 0<x<l₁, M=−Px

[0155] (when x=0, M=0, and when x=l₁, M=−Pl₁)

[0156] When l₁<x<l₁+l₂, M=−Px+P(x−l₁)=−Pl₁

[0157] When l₁+l₂<x<2l₁+l₂M=−P(2l₁+l₂−x)

[0158] (when x=l₁+l₂, M=−Pl₁, and when x=2l₁+l₂, M=0)

[0159] (Flexure) $\begin{matrix}{{{{With}\quad {respect}\quad {to}\quad 0} \leq x \leq l_{1}},{\frac{^{2}y}{x^{2}} = {{- \frac{M}{EI}} = \frac{Px}{EI}}}} & (1) \\{{\therefore\frac{y}{x}} = {\frac{{Px}^{2}}{2{EI}} + C_{1}}} & (2) \\{{\therefore y} = {\frac{{Px}^{2}}{6{EI}} + {C_{1}x} + C_{2}}} & (3) \\{{{{With}\quad {respect}\quad {to}\quad l_{1}} \leq x \leq {l_{1} + l_{2}}},{\frac{^{2}y}{x^{2}} = \frac{{Pl}_{1}}{EI}}} & (4) \\{{\therefore\frac{y}{x}} = {{\frac{{Pl}_{1}}{2{EI}}x} + C_{3}}} & (5) \\{{\therefore y} = {{\frac{{Pl}_{1}}{2{EI}}x^{2}} + {C_{3}x} + C_{4}}} & (6)\end{matrix}$

[0160] With respect to l₁+l₂≦x≦2l₁+l₂, M=−P(2l₁+l₂−x), and hence, if itis assumed that x′=2l₁+l₂−x, M=−Px′ $\begin{matrix}{\frac{^{2}y}{x^{2}} = {\frac{^{2}y}{x^{\prime 2}} = \frac{{Px}^{\prime}}{EI}}} & (7) \\{{\therefore\frac{y}{x^{\prime}}} = {\frac{{Px}^{\prime 2}}{2{EI}} + C_{5}}} & (8) \\{{\therefore y} = {\frac{{Px}^{\prime 3}}{6{EI}} + {C_{5}x^{\prime}} + C_{6}}} & (9)\end{matrix}$

[0161] The boundary conditions are:

[equ.(2)]_(x=l) ₁ =[equ.(5)]_(x=l) ₁   (10)

[equ.(3)]_(x=l) ₁ =0  (11)

[equ.(6)]_(x=l) ₁ =0  (12)

[0162] Since the opposite side is also symmetrical, $\begin{matrix}{\lbrack {{equ}.\quad (5)} \rbrack_{x = {l_{1} + \frac{l_{2}}{2}}} = 0} & (13)\end{matrix}$

 c₁=c₅  (14)

c₂=c₆  (15).

[0163] From the above,

[0164] when 0≦x≦l₁, $\begin{matrix}\begin{matrix}{y = {\frac{{Px}^{3}}{6{EI}} - {\frac{{Pl}_{1}( {l_{1} + l_{2}} )}{2{EI}}x} + \frac{{Pl}_{1}^{2}( {{2l_{1}} + {3l_{2}}} )}{6{EI}}}} \\{{{{when}\quad l_{1}} \leq x \leq {l_{1} + l_{2}}},}\end{matrix} & (16) \\\begin{matrix}{y = {{\frac{{Pl}_{1}}{2{EI}}x^{2}} - {\frac{{Pl}_{1}( {{2l_{1}} + l_{2}} )}{2{EI}}x} + \frac{{Pl}_{1}^{2}( {l_{1} + l_{2}} )}{2{EI}}}} \\{{{{{and}\quad {when}\quad l_{1}} + l_{2}} \leq x \leq {{2l_{1}} + l_{2}}},}\end{matrix} & (17) \\{y = {{\frac{P}{6{EI}}( {{2l_{1}} + l_{2} - x} )^{3}} - {\frac{{Pl}_{1}( {l_{1} + l_{2}} )}{2{EI}}( {{2l_{1}} + l_{2} - x} )} + \frac{{Pl}_{1}^{2}( {{2l_{1}} + {3l_{2}}} )}{6{EI}}}} & (18)\end{matrix}$

[0165] Since a section at the time of x=0 is the bending quantity,

[0166] when 0≦x≦l₁, $\begin{matrix}{\delta = \frac{{Pl}_{1}^{2}( {{2l_{1}} + {3l_{2}}} )}{6{EI}}} & \quad \\{{\therefore P} = {\frac{6{EI}\quad \delta}{l_{1}^{2}( {{2l_{1}} + {3l_{2}}} )}.}} & (20)\end{matrix}$

[0167] From equations (20) and (16), $\begin{matrix}{y = {{\frac{\quad \delta}{l_{1}^{2}( {{2l_{1}} + {3l_{2}}} )}x^{3}} + \frac{3{\delta ( {l_{1} + l_{2}} )}}{l_{1}^{2}( {{2l_{1}} + {3l_{2}}} )} + \delta}} & (21)\end{matrix}$

[0168] When l₁≦x≦l₁+l₂,

[0169] from equations (20) and (17), $\begin{matrix}{y = {{\frac{\quad {3\delta}}{l_{1}( {{2l_{1}} + {3l_{2}}} )}x^{2}} + {\frac{3{\delta ( {{2l_{1}} + l_{2}} )}}{l_{1}( {{2l_{1}} + {3l_{2}}} )}x} + \frac{3{\delta ( {l_{1} + l_{2}} )}}{{2l_{1}} + {3l_{2}}}}} & (22)\end{matrix}$

[0170] When l₁+l₂<x<2l₁+l₂,

[0171] from equations (20) and (18), $\begin{matrix}{y = {{\frac{\quad \delta}{l_{1}^{2}( {{2l_{1}} + {3l_{2}}} )}( {{2l_{1}} + l_{2} - x} )^{3}} + {\frac{3{\delta ( {l_{1} + l_{2}} )}}{l_{1}( {{2l_{1}} + {3l_{2}}} )}( {{2l_{1}} + l_{2} - x} )} + {\delta.}}} & (23)\end{matrix}$

[0172] The equations (21), (22) and (23) indicate deformations of thereticle due to the stress P. Therefore, if the shape of the reticle inthe state with no stress applied is the shape expressed by the equation(21), (22) or (23), the reticle can be corrected to have a completeplane by applying the stress P on the opposite side, as shown in FIG.23.

[0173] As shown in FIG. 23, when supporting portions {circle over (1)},{circle over (1)}′ and {circle over (2)}, {circle over (2)}′ areprovided, deformation is terminated at the point in time when thesurface to be attracted of the reticle comes in contact with thesupporting portions {circle over (1)}, {circle over (1)}′ and {circleover (2)}, {circle over (2)}′. Therefore, it is not always necessary tosatisfy equation (20), and it is only necessary to satisfy equation (24)described below. However, it is necessary that δ is in the formexpressed by equation (21), (22) or (23). $\begin{matrix}{\delta < \frac{{Pl}_{1}^{2}( {{2l_{1}} + {3l_{2}}} )}{6{EI}}} & (24)\end{matrix}$

[0174] Since a vacuum chuck is normally used for holding the reticle,the stress P has a value obtained by multiplying the atmosphericpressure by the attraction area. Normally, the area of the interval l₁between the supporting points is the attraction area.

[0175] Moreover, since the frictional force is important in the reticleholder for the scanning type exposure apparatus, the reticle holder isdesigned to have a large attraction area. A preferable design example inthis case is shown in FIG. 24. The supporting points {circle over (3)},{circle over (3)}′ are provided outside of the supporting points {circleover (2)}, {circle over (2)}′, and the attraction area is increasedrespectively by the area l₃ from {circle over (2)} to {circle over (3)}and {circle over (2)}′ to {circle over (3)}′. As a result, largerattraction and frictional force can be obtained.

[0176] The peripheral part of the reticle such as the area l₃ hasnormally poor flatness, and if the supporting point is brought intocontact with these areas l₃, the reticle R bends largely. Therefore, itis necessary to avoid contact therebetween. For example, as with thereticle shape indicated by the dotted line in FIG. 24, a taper isprovided at the end of the reticle R, and machining may be performed sothat the surface to be attracted of the reticle after attraction shownby the solid line is away from the supporting points {circle over (3)},{circle over (3)}′. This clearance (set back amount) h is preferably notlarger than 5 μm. Since the surface precision in the area l₃ is rough,as compared with the surface precision in the area l₂ (normally notlarger than 500 nm), machining of the area l₃ is easy.

[0177] When the state shown in FIG. 24 is explained by using a generalexpression, the shape of the precision warrantable area l₄ on theattracted surface of the reticle satisfies the relations expressed byequations (21), (22). (23) and (24), and a following equation (25)should be satisfied at the supporting points {circle over (3)}, {circleover (3)}′. $\begin{matrix}\begin{matrix}{{{When} - l_{3}} = {x\quad {or}}} \\{x = {{2l_{1}} + l_{2} + l_{3}}} \\{y < {{\frac{\quad \delta}{l_{1}^{2}( {{2l_{1}} + {3l_{2}}} )}( {- l_{3}} )^{3}} + {\frac{3{\delta ( {l_{1} + l_{2}} )}}{l_{1}( {{2l_{1}} + {3l_{2}}} )}( {- l_{3}} )} + \delta}}\end{matrix} & (25)\end{matrix}$

[0178] A similar effect can be obtained by shaving the portionscorresponding to the supporting points {circle over (3)}, {circle over(3)}′ by about 5 μm in depth, instead of making the area l₃ on thesurface to be attracted of the reticle set back. Moreover, it is alsopossible to make both the area l₃ on the surface to be attracted of thereticle and the portions corresponding to the supporting points {circleover (3)}, {circle over (3)}′ set back, respectively.

[0179] In the first and the second embodiments, after the reticle isattracted and held, the pattern face of the reticle slightly bends dueto gravity (self weight). However, since this quantity can be calculatedbeforehand, the curvature of field occurring due to bending of thepattern face of the reticle can be corrected, by driving a movable lensgroup in the projection optical system.

[0180] According to the holding method of the present invention, thefirst area having predetermined surface precision and the second areaother than the first area, of the surface to be attracted, can berespectively attracted and held separately by the first holding sectionand the second holding section. As a result, the first holding sectioncan stably hold a sample without deteriorating the overall surfaceprecision of the sample, and the second holding section can increase thewhole surface of the sample to be attracted, thereby enabling stableretention.

What is claimed is:
 1. A holding apparatus which holds a surface to beattracted of a flat sample, comprising: a first holding section facing afirst area having predetermined surface precision of the surface to beattracted; a second holding section facing a second area other than thefirst area of the surface to be attracted; and a suction apparatus whichdraws out gas in spaces between the surface to be attracted and thefirst and the second holding sections.
 2. A holding apparatus accordingto claim 1, wherein the suction apparatus comprises: a first suctiondevice which draws out gas in the space between the surface to beattracted and the first holding section; and a second suction devicewhich draws out gas in the space between the surface to be attracted andthe second holding section.
 3. A holding apparatus according to claim 1,wherein each of the first holding section and the second holding sectionare arranged at a plurality of positions with respect to the surface tobe attracted.
 4. A holding apparatus according to claim 1, wherein thefirst holding section and the second holding section are arrangedadjacent to each other, and a boundary portion between the first holdingsection and the second holding section is arranged at least in the firstarea.
 5. A holding apparatus according to claim 1, wherein the firstholding section and the first area come in contact with each other, andthe second holding section and the second area are set to have apredetermined gap.
 6. A holding apparatus according to claim 1, whereinthe first area is a planar portion formed on a substantially centralportion of the surface to be attracted, and the second area is a taperportion formed on the outside of the central portion in a direction awayfrom the second holding section towards the outside from the centralside.
 7. A holding apparatus according to claim 1, wherein a heightposition of the second holding section is set corresponding to the shapeof the surface to be attracted.
 8. A holding apparatus according toclaim 1, wherein a height position of the second holding section is setto a position lower than the first holding section with respect to thesurface to be attracted.
 9. A holding apparatus according to claim 1,wherein there is provided a control apparatus which separately controlsa suction amount of gas per unit time by the first suction device and asuction amount of gas per unit time by the second suction device.
 10. Aholding apparatus according to claim 1, wherein the suction amount ofgas per unit time by the first suction device is set greater than thesuction amount of gas per unit time by the second suction device.
 11. Aholding apparatus according to claim 1, wherein an area of the firstholding section with respect to the first area is set larger than anarea of the second holding section with respect to the second area. 12.A holding apparatus according to claim 1, having a pin and chuck holder,and the first holding section and the second holding section are suctionpads of the pin and chuck holder.
 13. A holding method for holding asurface to be attracted of a flat sample, wherein each of a first areahaving a predetermined surface precision of the surface to be attractedand a second area other than the first area of the surface to beattracted are attracted and held by a first holding section and a secondholding section, respectively and independently.
 14. A holding methodaccording to claim 13, wherein the holding is performed while having apredetermined gap between the second holding section and the secondarea.
 15. A holding method according to claim 13, wherein an area of thefirst holding section with respect to the first area is set larger thanan area of the second holding section with respect to the second area.16. An exposure apparatus which exposes a pattern of a mask held by amask holder onto a substrate held by a substrate holder, wherein theholding apparatus according to claim 1 is used for at least one of themask holder and the substrate holder.
 17. A device manufacturing methodincorporating a lithography process, wherein the exposure apparatusaccording to claim 16 is used in the lithography process.
 18. A maskholding method for holding a mask in which a surface to be attracted hasa convex shape towards a first direction within a predeterminedallowable range, with a pair of first attraction holding sectionsarranged opposing the first direction, wherein the mask is held so as tosatisfy the following relational expression: δ<Pl ₁ ²(2 l ₁+3 l ₂)/6EIwhere l₁ respectively denotes an interval between a central supportingpoint and an outside supporting point of the mask in the respectivefirst attraction holding sections, l₂ denotes an interval between thecentral supporting points in the respective first attraction holdingsections, δ denotes an interval between the outside supporting point andthe mask, which is generated when the mask is mounted on the centralsupporting point, P denotes a product of the atmospheric pressure and anattraction area of the first attraction holding section, E denotes amodulus of longitudinal elasticity of the mask, and I denotes ageometrical moment of inertia of the mask.
 19. A mask holding methodaccording to claim 18, wherein a surface precision warrantable area inthe mask attraction surface is held using the first attraction holdingsection, and other than the surface precision warrantable area is heldby the second attraction holding section.
 20. A mask holding methodaccording to claim 19, wherein after attracting the mask using the firstattraction holding section, the mask is held so as to have apredetermined gap between the second attraction holding section and themask.
 21. A mask holding apparatus which holds a mask in which a surfaceto be attracted has a convex shape towards a first direction within apredetermined allowable range, with a pair of first attraction holdingsections arranged opposing the first direction, wherein the firstattraction holding sections are respectively arranged so as to satisfythe following relational expression: δ<Pl ₁ ²(2l ₁+3l ₂)/6EI where l₁respectively denotes an interval between a central supporting point andan outside supporting point of the mask in the respective firstattraction holding sections, l₂ denotes an interval between the centralsupporting points in the respective first attraction holding sections, δdenotes an interval between the outside supporting point and the mask,which is generated when the mask is mounted on the central supportingpoint, P denotes a product of the atmospheric pressure and an attractionarea of the first attraction holding section, E denotes a modulus oflongitudinal elasticity of the mask, and I denotes a geometrical momentof inertia of the mask.
 22. A mask holding apparatus according to claim21, wherein a surface precision warrantable area in the mask attractionsurface is held using the first attraction holding section, and furtherhaving a second attraction holding section which holds other than thesurface precision warrantable area.
 23. A mask holding apparatusaccording to claim 22, wherein after attracting the mask using the firstattraction holding section, the mask is held so as to have apredetermined gap between the second attraction holding section and themask.
 24. A holding apparatus which holds a surface to be attracted of aflat sample, having a holding section for attracting and holding aperipheral part of the flat sample, wherein the holding sectioncomprises: a first holding section which is brought into contact with asurface to be attracted of the sample, to attract the sample; and asecond holding section arranged further to the outside of the samplethan the first holding section, and having a small gap with the surfaceto be attracted of the sample so as to suppress distortion in thesurface to be attracted of the sample on the inside from the firstholding section.
 25. A holding apparatus according to claim 24, whereinthe holding section comprises a partition section for forming the firstholding section and the second holding section, and a plurality of pinmembers arranged on an inside of the partition section.
 26. A holdingapparatus according to claim 24, wherein a suction section of the secondholding section is arranged lower than a suction section of the firstholding section.
 27. A holding apparatus according to claim 24, whereina suction section of the second holding section is communicated with asuction section of the first holding section, and further having asuction apparatus which sucks the suction section of the second holdingsection together with the suction section of the first holding section.28. An exposure apparatus which exposes a pattern of a mask held by amask holder onto a substrate, wherein the holding apparatus according toclaim 24 is used for the mask holder.
 29. A holding apparatus whichholds a surface to be attracted of a flat sample, having a holdingsection for attracting and holding a peripheral part of the flat sample,wherein the holding section comprises: a first holding section which isbrought into contact with a surface to be attracted of the sample, toattract the sample; and a second holding section arranged further to theoutside of the sample than the first holding section, and with a suctionsection arranged lower than the first holding section.
 30. An exposureapparatus which exposes a pattern of a mask held by a mask holder onto asubstrate, wherein the holding apparatus according to claim 29 is usedfor the mask holder.